Light sources

Abstract

A light source arranged to be illuminated automatically upon failure of the normal electricity supply to a room, building or the like. The light source comprises a lamp housing containing a bulb, batteries and switch, and a base on which the lamp housing can be mounted. One part of an electromagnet including an energizing winding is mounted in the base and the other part is mounted in the torch housing such that when the housing is mounted on the base and an a.c. supply is made to the base, the two parts of the electromagnet are mutually attracted and the housing is held securely on the base. If the a.c. supply is interrupted the electromagnet is de-energized, allowing the housing to be removed from the base and, at the same time, the switch is operated to connect the batteries to supply current to the bulb.

I claim as my invention: 
     
       1. A light source comprising a lamp bulb, an electrical power source for illuminating the lamp bulb, a housing for containing said lamp bulb and said power source, a surface for supporting said housing, switch means for selectively coupling the power source to said bulb, control means for controlling said switch means, said control means being coupled to and operated by an a.c. supply such that when said housing is mounted on the supporting surface and the a.c. supply is maintained, said power source is disconnected from the bulb, and when the a.c. supply is interrupted, said power source is connected to illuminate the bulb, means for securing said housing on said supporting surface, the securing means comprising transformer means having a magnetically attractable component and a magnetically attracting component, one of the components mounted on said supporting surface and the other of said components mounted in said housing, means coupling the a.c. supply to said transformer means to produce magnetic forces between said components, such magnetic forces being sufficient to secure said housing on said supporting surface but allowing manual separation of said housing from said supporting surface whether the a.c. supply is maintained or interrupted. 
     
     
       2. The light source according to claim 1 wherein said control means includes switching means for automatically connecting said power source to illuminate said bulb when said housing is removed from the mounting means. 
     
     
       3. A light source according to claim 2, wherein a transformer couples said a.c. supply to the control means. 
     
     
       4. A light source according to claim 3, wherein said securing means comprises an electromagnet fixedly mounted in one of said mounting means or said housing and arranged to be energized by the a.c. supply through said circuit means, said attraction means comprising a soft iron pole piece, fixedly secured and so arranged in the other of the housing or mounting means whereby, when the housing is mounted on the mounting means and the a.c. supply is connected, the electromagnet attracts the attractable component and thus secures the housing to the mounting means. 
     
     
       5. The light source according to claim 1 wherein said power source comprises a rechargeable battery and said control means includes circuitry for supplying a charging current derived from the a.c. supply to said battery when the a.c. supply is coupled thereto and said housing is mounted on said mounting means. 
     
     
       6. A light source according to claim 5, in which said switch means connects said battery to said bulb when the a.c. source is disconnected or said housing is removed from said mounting means and connects said battery to a said circuitry when said housing is mounted on said mounting means and the a.c. supply is connected. 
     
     
       7. A light source according to claim 4, wherein said electromagnet is mounted in said mounting means and is arranged with a part upstanding therefrom to engage in a recess formed in the housing, the attraction means mounted proximate the inner end of the recess. 
     
     
       8. A light source according to claim 1 wherein the switch means comprises a relay. 
     
     
       9. The light source according to claim 1 wherein said attracting component is formed by one part of a split magnetic core mounted stationary in one of the mounting means or said supporting surface, and further wherein said attractable component is formed by the other part of said split magnetic core fixedly secured in the other of the housing or said supporting surface. 
     
     
       10. The light source as claimed in claim 9 wherein said other component is a magnetic core having an aperture therein and further wherein said one component comprises a magnetic core having an elongate member extending therethrough to mate with said aperture. 
     
     
       11. A light source according to claim 9, in which the said one part of said core is mounted within the mounting means and includes a part projecting therefrom to engage in a recess formed within said attraction component.